The Modulatory Mechanism Of Orexin Receptor 1 In The VTA On Anxiety-like Behaviors Induced By Morphine Withdrawal

Background One negative emotional state from morphine protracted abstinence is anxiety which can drive craving and relapse risk in opioid addicts.Although the orexinergic system has been reported to be important in mediating emotion processing and addiction,the role of orexinergic system in anxiety from drug protracted abstinence remains elusive.This suggests that OX1R in VTA plays an important role in regulating morphine-induced anxiety-like behavior.The Ventral Tegmental Area(VTA),as an important brain region of the mesencephalic limbic dopamine system,receives a large number of orexin signals from the Lateral Hypothalamus(LH).In recent years,VTA has been found to play an important role in the regulation of drug addiction and emotional disorders.Therefore,we speculate that orexin may play an important role in regulating morphine-induced anxiety in VTA.Objective To explore the mechanism of orexin regulating morphine-induced anxiety-like behavior in the ventral tegmental area(VTA)by using behavioral test,transmission electron microscope,electrophysiology and virus-mediated regulation of orexin type 1 receptor(OX 1R).Methods Adeno-associated virus was injected into the VTA of C5 7 adult male mice by using stereotactic microinjection,and the anxiety-like behavior of the mice was respectively observed after knockdown or overexpress ion of orexin type 1 receptor in the VTA.(2)TEM was used to observe the changes of neuronal structure and peripheral synapses in VTA after 3 days of morphine withdrawal,7 days of continuous morphine injection and overexpression of OX1R in VTA.(3)Patch clamp and pharmacological methods were used to investigate the changes of neuronal discharge activity in VTA after morphine withdrawal.Results(1)Virus-mediated knockdown of OX1R in the VTA prevented morphine abstinence-induced anxiety-like behaviors and virus-mediated overexpression of OX1R in the VTA was sufficient to produce anxiety-like behaviors in male mice.(2)Chronic morphine treatment resulted in the structural damage of VTA neurons.Morphine Withdrawal lead to a decrease in the number of synapses around neurons,while the overexpression of OX1R in VTA resulted in the structural damage of neurons.(3)The VTA neuronal activity was increased significantly induced by morphine protracted abstinence,which was mediated by OX1R.Conclusion This study in further reveals OX1R plays a critical role in the anxiety-like behaviors during morphine protracted-abstinence.The OX1R receptor may be a target to intervene morphine abstinence-induced anxiety.